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What metrics for what panel Pre-recruited probability-based online panels Response rates can be calculated because the frame is known (AAPOR, 2006) Volunteer opt-in panels Response rates cannot be computed (AAPOR, 2007) However, other metrics can be calculated, e.g. completion rate 1

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2 Current status Volunteer, non-probability (opt-in) panels, widely used in market research, outnumber probability-based Web panels More and more probability-based online panels being built American National Election Studies (ANES) Panel Face-to-Face Recruited Internet Survey Platform (FFRISP, 2008) Dutch Long-term Internet Study for the Social Science (LISS) panel (2007) Still no officially agreed standard on how to compute response rates for online panels

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Review of current standards Many efforts and proposals by different national and international organizations: European Society for Opinion and Marketing Research – ESOMAR European Federation of Associations of Market Research Orgs. –EFAMRO Interactive Marketing Research Organization – IMRO Advertising Research Association – ARF quality initiative Bob Lederer proposal endorsed by the American Marketing Association (AMA) Latest effort by ISO (standard #26362) touches on subject 3

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Some journals are giving guidelines on how response rates should be computed specifically for online surveys (not necessarily online panels) Journals enforcing AAPOR standards: (e.g. POQ, IJPOR…) Journal of Medical Internet Research Journal of Medical Internet Research (Eysenbach, 2004): Journal recommendations 4 In online surveys, there is no single response rate. Rather, there are multiple potential methods for calculating a response rate, depending on what are chosen as the numerator and denominator. As there is no standard methodology, we suggest avoiding the term response rate and have defined how, at least in this journal, response metrics such as, what we call, the view rate, participation rate and completion rate should be calculated.

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ESOMAR and IMRO examples ESOMAR (2005) metrics: Response based on the total amount of invites (% of full numbers) per sample drawn (country, questionnaire) % questionnaire opened % questionnaire completed (including screen-out) % in target group (based on quotas) % validated (the balance is cleaned out, if applicable) (p. 20). IMRO (2006) metrics: Response rate is based on the people who have accepted the invitation to the survey and started to complete the survey. Even if they are disqualified during screening, the attempt qualifies as a response (p. 13). Completion rate is calculated as the proportion of those who have started, qualified, and then completed the survey (p. 13). 5

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ISO 26362:2009 Participation rate: number of panel members who have provided a usable response divided by the total number of initial invitations requesting members to participate (p. 3) Usable response is one where the respondent has provided answers to all the questions required by the survey design The term response rate cannot be used to describe respondent cooperation for access panels 7

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Necessary information to compute response metrics In order to compute response metrics for online panels we need to understand how panel members are recruited and what stages are used to build a panel Volunteer-opt-in design Probability-based design 8

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Common steps in building a probability- based panel 1.Recruitment Rate (RECR): the recruitment of potential panel members Recruitment rate calculation will depend on the recruitment mode: face -to-face, telephone, mail 2.Profile Rate (PROR): empanelling recruited persons This stage counts panel members that answered their profile survey, generally a questionnaire collecting background information and welcoming respondents to the panel The computation of the profile rate (a.k.a., connection rate) will depend on the data collection mode Profiled members are considered to be active members in the pool from which study samples can be drawn 12

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The computation of a CUMRR is straightforward when the panel is built with a single recruitment cohort Computing CUMRR with 1 cohort 23 Study Respondents RECR PRORRETR COMR

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Unequal cohort contributions to a study sample selected from among all active members 24 Computing CUMRR with 3 cohorts

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Formulas dealing with multiple cohorts (1.) RECR, PROR, RETR are calculated as the weighted average of the size contribution of each cohort Example to calculate RECR total 25 Where W cn = the number of cases contributed to the sample from cohort n

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Computing completion rate (COMR) when multiple data collection modes are used Completion rates need to be computed separately for each mode Web survey Mail, phone or IVR These rates should also be combined as a weighted average 29

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Technical condition in order to compute response metrics In order to compute response metrics each panel organization must keep an historical database with rates for each member More specifically for probability-based online panels it is necessary that: Each panel member ever recruited must have a record of his/her: –Recruitment rate cohort value –Profile rate cohort value –Retention rate cohort value 30